Abstract
Strongly correlated vanadium dioxide (VO2) is one of the most promising materials that exhibits a temperature-driven, metal-insulator transition (MIT) near room temperature. The ability to manipulate the MIT at nanoscale offers both insight into understanding the energetics of phase transition and a promising potential for nanoelectronic devices. In this work, we study nanoscale electrochemical modifications of the MIT in epitaxial VO2 thin films using a combined approach with scanning probe microscopy (SPM) and theoretical calculations. We find that applying electric voltages of different polarity through an SPM tip locally changes the contact potential difference and conductivity on the surface of VO2 by modulating the oxygen stoichiometry. We observed nearly 2 orders of magnitude change in resistance between positive and negative biased-tip written areas of the film, demonstrating the electric field modulated MIT behavior at the nanoscale. Density functional theory calculations, benchmarked against more accurate many-body quantum Monte Carlo calculations, provide information on the formation energetics of oxygen defects that can be further manipulated by strain. This study highlights the crucial role of oxygen vacancies in controlling the MIT in epitaxial VO2 thin films, useful for developing advanced electronic and iontronic devices.
Original language | English |
---|---|
Pages (from-to) | 7159-7166 |
Number of pages | 8 |
Journal | ACS Nano |
Volume | 12 |
Issue number | 7 |
DOIs | |
State | Published - Jul 24 2018 |
Funding
This work was supported by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division (synthesis) and as part of the Computational Materials Sciences Program (characterization and theory). Scanning probe microscopy and scanning transmission electron microscopy studies were performed as user projects at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory (ORNL) by the Scientific User Facilities Division, BES, DOE. This research used resources of the Oak Ridge Leadership Computing Facility at ORNL, which is supported by the Office of Science of the DOE under Contract DE-AC05-00OR22725. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of DOE under Contract DE-AC02-05CH11231.
Keywords
- density functional theory
- metal-insulator transition
- oxygen vacancy
- quantum Monte Carlo
- scanning probe microscopy
- vanadium dioxide